BUG #12670: Can't create postgis extension in single-user mode

The following bug has been logged on the website:

Bug reference: 12670
Logged by: Михаил Доронин
Email address: warrior2031(at)mail(dot)ru
PostgreSQL version: 9.3.5
Operating system: ubuntu
Description:

Some guy in your IRC told me this after some inquire.

RhodiumToad: Guest78493: in single-user, doing CREATE TYPE ... AS ...;
doesn't create the array type

RhodiumToad: Guest78493: it creates only the non-array one, but I have no
idea yet why

RhodiumToad: Guest78493: so for now, any extension with a CREATE TYPE AS
won't load correctly in single-user

RhodiumToad: Guest78493: arguably if it doesn't work it should error rather
than quietly getting it wrong, so I think you're justified in calling it a
postgres bug

Please don't hesitate to ask any additional information.